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The Jovian Ionospheric Alfvén Resonator and Auroral Particle Acceleration
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  • Robert L. Lysak,
  • Yan Song,
  • Sadie Suzanne Elliott,
  • William S Kurth,
  • Ali H. Sulaiman,
  • Daniel J Gershman
Robert L. Lysak
University of Minnesota

Corresponding Author:[email protected]

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Yan Song
University of Minnesota
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Sadie Suzanne Elliott
University of Minnesota
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William S Kurth
University of Iowa
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Ali H. Sulaiman
University of Iowa
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Daniel J Gershman
NASA Goddard Space Flight Center
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Abstract

The ionospheric Alfvén resonator (IAR) is a structure formed by the rapid decrease in the plasma density above a planetary ionosphere. This results in a corresponding increase in the Alfvén speed that can provide partial reflection of Alfvén waves. At Earth, the IAR on auroral field lines is associated with the broadband acceleration of auroral particles, sometimes termed the Alfvenic aurora. This arises since phase mixing in the IAR reduces the perpendicular wavelength of the Alfvén waves, which enhances the parallel electric field due to electron inertia. This parallel electric field fluctuates at frequencies of 0.1-20.0 Hz, comparable to the electron transit time through the region, leading to the broadband acceleration. The prevalence of such broadband acceleration at Jupiter suggests that a similar process can occur in the Jovian IAR. A numerical model of Alfvén wave propagation in the Jovian IAR has been developed to investigate these interactions. This model describes the evolution of the electric and magnetic fields in the low-altitude region close to Jupiter that is sampled during Juno’s perijove passes. In particular, the model relates measurement of magnetic fields below the ion cyclotron frequency from the MAG and Waves instruments on Juno and electric fields from Waves to the associated parallel electric fields that can accelerate auroral particles.